S10 or S18 of pulp samples were determined according to TAPPI T 235 cm-00 using sodium hydroxide solution of 10% or 18% for the extraction.
The molecular weight distribution of samples was determined on LC Biotin gel permeation chromatography (Waters 600E), equipped with a differential refractometer detector (Waters 410); columns were Waters Styragel HT6E. Prior to the determination, sample was firstly dissolved in the 8% LiCl/ DMAc solution. The mobile phase of 0.5% LiCl/DMAc was pumped into the system at a flow rate of 1 mL/min; the system was operated at column temperature of 55 °C; the injection volume was 10 μL.
3. Results and discussion
3.1. Cellulase adsorption ratio
The amount of cellulase adsorption is known to affect the enzymatic treatment efficiency. Increasing pulp consistency increases the interactions of cellulase and cellulose, therefore, improving the cellulase adsorption onto cellulose fibers. The cellulase adsorption ratio was 59%, 74% and 83% for pulp consistency of 3%, 10% and 20%, respectively. These results were in agreement with the hypothesis that higher pulp consistency will lead to higher cellulase adsorption. Similarly, Várnai et al. (2013) also observed the increases of cellulase adsorption ratio from 50% to 90% at the substrate concentration increases from 1% to 20% during the Avicel bioconversion process.